A known dog clutch device disclosed in JP2010-96190A (which will be hereinafter referred to as Reference 1) includes a rotary shaft, a hub (clutch hub), a sleeve, and a clutch ring. The dog clutch device is configured as described below in order to achieve high engagement and in order to reduce gear backlash. The sleeve slidably engages with the clutch hub in an axial direction of the rotary shaft. A spline of the sleeve is engageable with a dog clutch portion of the clutch ring rotatably arranged relative to the clutch hub. The spline of the sleeve includes first and second teeth. A length (whole depth) of each of the first teeth in a radial direction of the sleeve is designed to be longer than (greater than) a length (whole depth) of each of the second teeth in the radial direction. The first and second teeth will be hereinafter referred to as high and short teeth. The dog clutch portion of the clutch ring includes forward and rearward teeth (clutch forward and rearward teeth). Each of the clutch forward teeth includes a length (whole depth) in a radial direction of the clutch ring so as to engage with the high tooth of the spline and so as not to engage with the short tooth of the spline. Each of the clutch rearward teeth is provided at a position retracted from the clutch forward tooth in the axial direction. The clutch rearward tooth includes a length (whole depth) in the radial direction of the clutch ring so as to engage with the short tooth of the spline. A large-depth tooth groove with which the high tooth is engageable is formed between the clutch forward tooth and the clutch rearward tooth.
According to the dog clutch device disclosed in Reference 1, for example, in a case where a rotational difference between the clutch ring and the sleeve that is engaged with the clutch hub is large, the high tooth of the sleeve is firstly pressed against a flat surface serving as a front end surface of the clutch forward tooth of the clutch ring, therefore generating a frictional force. Rotating speeds of the clutch ring and the sleeve are increased and decreased depending on the frictional force, therefore reducing the rotational difference between the clutch ring and the sleeve. Accordingly, the rate of reduction of the rotational difference is small. Consequently, it takes time to obtain a condition where the sleeve rotating at a different speed relative to the clutch ring is brought into synchronized rotation with the clutch ring so that the high tooth of the sleeve shifts to be inserted in the large-depth tooth groove formed between the forward and rearward teeth of the clutch ring. As a result, gear-shifting time based on an operation of the dog clutch device is elongated.
A need thus exists for a dog clutch for an automated transmission, which is not susceptible to the drawback mentioned above.